ICTS_Denmark/Assets/FacebookSDK/link.xml

<linker>
  <assembly fullname="Facebook.Unity.Android" ignoreIfMissing="1">
    <type fullname="Facebook.Unity.Android.*" preserve="all"/>
  </assembly>
  <assembly fullname="Facebook.Unity.IOS" ignoreIfMissing="1">
    <type fullname="Facebook.Unity.IOS.*" preserve="all"/>
  </assembly>
</linker>